Thanks for the replies.
I had always assumed (for intracellular recordings) that damage to the cell
was the most likely candidate, although the odd paper does explicitly
mention the effect due to recording site.
For example, in recordings from antennal lobe neurons in the moth Manduca
sexta, Matsumoto and Hildebrand (Proc R Soc Lond B 213, 249-277 (1981)) make
"Action potentials recorded from the cell bodies typically had amplitudes
between 40 and 60mv and were non-overshooting (the resting potential was
usually -65 to -70mV) suggesting that action potentials did not actively
invade the cell bodies"
I quote this because this is probably the most informative comment I have
seen in any paper :)
That's not to say that some other gems remain undiscovered. To this end,
does anyone know of any papers/books that quantify the variability in
recorded amplitudes due to damage to the cell? - ie some sort of critique on
I realise, of course, that with damage there will be a continuum from
nothing to very high, but, for all practicle purposes, is there some typical
(amplitude) threshold above which neurophysiologists say "yep this one's
I think some statistics of this sort would be important to know, because
only then would one be able to say, with some confidence, that variability
in the size of action potentials, from one neuron type to another, is due to
intrinsic channel variations (density, kinetics), as opposed to limitations
in the recording technique.
It may well be that there are too many factors at play - my gut feeling is
that there may be. Either way, the answer is informative.